Question

A vertically held bar magnet is dropped along the axis of a copper ring having a cut as shown in the diagram. The acceleration of the falling magnet is:

• A. zero
• B. less than \( g \)
• C. \( g \)
• D. greater than \( g \)

Hint:

A cut in the ring breaks the circuit and prevents eddy currents from forming, so the magnet falls freely with acceleration \( g \).

Answer 1

The Correct Option is C

When a bar magnet is dropped through a conducting loop (like a copper ring), the changing magnetic flux induces eddy currents in the ring. These eddy currents oppose the motion of the magnet (Lenz’s law), thus reducing its acceleration to less than \( g \). However, in this case, the copper ring has a cut, meaning the circuit is incomplete and no eddy current can be established. Since no current is induced, there is no magnetic opposing force acting on the magnet. As a result, the magnet experiences no additional force other than gravity, and hence falls with an acceleration equal to \( g \).